Three-Leaf Dart-Shaped Single-Crystal BN Formation Promoted by Surface Oxygen

TL;DR

This study reports the synthesis of three-leaf dart-shaped single-crystal hexagonal boron nitride on copper foil via atmospheric-pressure chemical vapor deposition, highlighting the role of surface oxygen in shaping the crystal morphology.

Contribution

It demonstrates a novel 3LD-shaped h-BN crystal formation method and reveals how surface oxygen influences growth kinetics and morphology.

Findings

Surface oxygen suppresses h-BN nucleation on Cu.

Oxygen lowers edge attachment energy, altering growth mode.

3LD-shaped h-BN crystals can reach 18 μm in size.

Abstract

Two-dimensional hexagonal boron nitride (h-BN) single crystals with various shapes have been synthesized by chemical vapor deposition over the past several years. Here we report the formation of three-leaf dart (3LD)-shaped single crystals of h-BN on Cu foil by atmospheric-pressure chemical vapor deposition. The leaves of the 3LD-shaped h-BN are as long as 18 {\mu}m and their edges are smooth armchair on one side and stepped armchair on the other. Careful analysis revealed that surface oxygen plays an important role in the formation of the 3LD shape. Oxygen suppressed h-BN nucleation by passivating Cu surface active sites and lowered the edge attachment energy, which caused the growth kinetics to change to a diffusion-controlled mode.